Field of the Invention
The invention pertains to the field of tensioners. More particularly, the invention pertains to a tensioner with stored energy.
Description of Related Art
During the operational lifetime of a chain or belt, the chain or belt elongates, causing an increase in slack, and the chain or belt is also subject to variations in tension, both of which reduce the operational efficiency and may cause loss of control. A tensioner is used to contact a strand of the chain or belt to maintain tension in the strand during operation of the chain or belt.
U.S. Pat. No. 7,901,309, entitled “Tensioner for a Timing Chain” and issued Mar. 8, 2011 to Lehtovaara et al., discloses a tensioner with a base plate and a pivot arm. One end of the pivot arm is pivotally mounted to the base plate for rotation about a first axis. A spring biases the pivot arm to rotate in a tensioning direction. A push rod assembly is pivotally mounted to the other end of the pivot arm. The push rod assembly is rotatable about a second axis extending parallel to the first axis. The push rod assembly frictionally engages the pivot arm, generating frictional forces counteracting and damping the spring bias. When the tensioning guide is forced to rotate in the tensioning direction, the acting moment arm of the push rod, causes the guide to rotate towards the endless drive. The acting moment arm is considerable longer at the end of the tensioning stroke than in the beginning of the stroke.
U.S. Pat. No. 8,052,559, entitled “Tensioner with Two Way Damper” and issued Nov. 8, 2011 to Wigsten et al., discloses a tensioner for a power transmission system with two tensioning arms operatively engaged with the strand of the chain or the belt of the power transmission system. The upper end of each tensioning arm is connected to a two way damper, which is pivotally mounted between the upper ends of the tensioning arms. When a pre-determined chain tension overload threshold is reached, the damper allows the tensioner to adjust the tension in the chain with minimal oscillations and minimal phase change variation. The tension overload threshold is the amount of torque required to overcome the coefficient of friction.
The above-mentioned references are hereby incorporated by reference herein.